The terms polymerized and polymerizable, as they are used in the present application, encompass the terms cross-linkable/cross-linked and grafted/graftable as they are defined in the art. For example, not only does the term polymerization include the combination of monomers and prepolymers to form oligomers and polymers, it also includes the attachment of oligomers and polymers by various bridging constituents (cross-linking) and the attachment to oligomers and polymers of side chains having various atomic constituents (grafting).
In some applications, the physical properties of polymerized and/or cross-linked material are extremely important. For example, fast-acting surgical adhesives, sealants, bioactive agent release matrixes and implants utilized in medical, surgical and other in vivo applications require close control of the polymerized and/or cross-linked material. These materials include, for example, alpha-cyanoacrylates disclosed in U.S. Pat. Nos. 5,328,687 to Leung et al., 3,527,841 to Wicker et al., 3,722,599 to Robertson, 3,995,641 to Kronenthal et al., 3,940,362 to Overhults and U.S. patent application Ser. No. 08/266,647. The subject matter of the foregoing references is incorporated herein by reference.
Typically, when used as adhesives and sealants, cyanoacrylates are applied in monomeric form to the surfaces to be joined or sealed, where typically, in situ anionic polymerization of the monomer occurs, giving rise to the desired adhesive bond with a seal. Implants, such as rods, meshes, screws, and plates, may be formed of cyanoacrylate polymers, formed typically by radical-initiated polymerization.
Efforts to increase the tissue compatibility of alpha-cyanoacrylates have included modifying the alkyl ester group of the cyanoacrylates. For example, increasing the alkyl ester chain link to form the higher cyanoacrylate analogs, e.g., butyl-2-cyanoacrylates and octyl-2-cyanoacrylates, has been found to improve biocompatibility but the higher analogs biodegrade at slower rates than the lower alkyl cyanoacrylates.
Other examples of modified alpha-cyanoacrylates used in biomedical applications include carbalkoxyalkyl, alpha-cyanoacrylates (see, for example, U.S. Pat. No. 3,995,641 to Kronenthal et al.), flurocyanoacrylates (see, for example, U.S. Pat. No. 3,722,599 to Robertson et al.), and alkoxyalkyl 2-cyanoacrylates (see, for example, U.S. Pat. No. 3,559,652 to Banitt et al.). Other efforts have included mixing alpha-cyanoacrylates with dimethyl methylenemalonate and higher esters of 2-cyanoacrylic acid (see, for example, U.S. Pat. No. 3,591,676 to Hawkins et al.).
In other efforts to increase the usefulness of alpha-cyanoacrylate adhesive compositions for surgical applications, certain viscosity modifiers have been used in combination with alkyl alpha-cyanoacrylate monomers, such as methyl alpha-cyanoacrylate. See, for example, U.S. Pat. Nos. 3,564,078 (wherein the viscosity modifier is poly (ethyl 2-cyanoacrylate)) and 3,527,841 (wherein the viscosity modifier is poly(lactic acid)).
In U.S. Pat. No. 5,328,687 to Leung et al., the entire contents of which are hereby incorporated by reference, the use of formaldehyde scavengers has been proposed to improve biocompatibility of the alpha-cyanoacrylate polymers, whose biodegradation produces formaldehyde, for use in in vivo applications. Additionally, in U.S. application Ser. No. 08/266,647, the entire contents of which are incorporated herein by reference, the biodegradation rate of alpha-cyanoacrylate polymer is accomplished by regulating the pH of an immediate in vivo environment of a biocompatible composition. It is also known that various compounds can affect polymerization of alpha-cyanoacrylate monomers, including acids to inhibit or slow polymerization (e.g., U.S. Pat. No. 3,896,077 to Leonard et al.), and bases to accelerate polymerization (e.g., U.S. Pat. No. 3,759,264 to Coover and U.S. Pat. No. 4,042,442 to Dombroski et al.).
Likewise, many polymerization and/or cross-linking inhibitors are conventionally added to polymerizable and/or cross-linkable materials in order to increase their shelf life. However, the amount of polymerization inhibitor that may be added to the polymerizable and/or cross-linkable material is limited due to the negative impact on any subsequent polymerization process. In particular, a large quantity or concentration of polymerization inhibitor that is added to stabilize polymerizable and/or cross-linkable material may stabilize the polymerizable and/or cross-linkable material to an extent that will adversely affect polymerization. Accordingly, conventional polymerizable and/or cross-linkable materials may contain only a limited amount of polymerization inhibitor.
For certain applications of polymerizable and/or cross-linkable material there exists a need for controlling the setting time of polymerizable and/or cross-linkable material. For example, surgical adhesives used for some surgical procedures require rapidly or relatively less rapidly setting polymerization materials, depending on the procedure involved (e.g., U.S. Pat. No. 5,328,687 to Leung et al. and U.S. application Ser. No. 08/266,647, the disclosures of which are incorporated herein by reference). Other bonding processes, including sealing and bonding processes in the construction and automotive industries, molding processes in the plastic industry, and coating processes in the textile and electronics industries, require a variety of setting times. Many of these applications require control of the setting time in order to facilitate adequate strength, elasticity and hardness of a polymerized material while also providing the necessary amount of working time to apply the polymerized material to a desired substrate.
Various dispensing devices have been developed for the purposes of applying and mixing multiple components simultaneously. For example, U.S. Pat. No. 3,468,548 to Leigh discloses a dispenser for dispensing two paste-like materials, such as creams or gels. One of the materials is stored in a tube and a second material is stored in a chamber of a nozzle attached to the tube. When the first material is forced from the tube, it flows through the nozzle and mixes with the second material.
U.S. Pat. No. 3,891,125 to Morane et al. describes a device for storing two products separately and mixing the products prior to application. One product is stored in a nozzle attached to a container containing a second product. The product in the nozzle drops by the force of gravity into the container containing the second product and mixing occurs. Subsequently, the mixed products may be forced from the container and applied to a suitable substrate.
U.S. Pat. No. 3,770,523 to Biswas relates the application of a thickened slurry explosive into a bore hole or a container. A stream of slurry explosive is thickened by admixing the stream with a cross-linking agent by plurality of jet streams impinging on the slurry stream.
U.S. Pat. No. 4,801,008 to Rich discloses a disposable cartridge including a chamber containing a plurality of inter-reacting components of an adhesive system. The components are separated from each other by a barrier film. They are expelled through a nozzle where they are mixed with a static mixing element.